In general, the present invention relates to computer storage enclosures containing Fast and Ultra SCSI (up to 40 Mbytes/sec, or MBps), Ultra2 (up to 80 MBps), and Ultra3 SCSI (up to 160 MBps) peripherals; and more particularly, to a new xe2x80x9cintelligentxe2x80x9d SCSI-compliant computer enclosure module having a control unit for manual or auto-configuration of two independently-operational SCSI buses (also operational as a single-unified SCSI bus), auto-termination circuitry capable of configuring (automatically or manually) the termination mode for each bus, and logic for setting a SCSI ID (i.e., the bit-significant representation of a SCSI address) for each device in communication with the SCSI bus(es).
The widely-used small computer system interface (SCSI) protocol was developed for industry groups, under the American National Standards Institute (ANSI) and International Standards Organization (ISO) guidelines, to provide an efficient peer-to-peer I/O bus. A main objective of the standardized protocol adopted for SCSI parallel interface is to provide host computers with device independence within a class of devices. Devices that conform with the mechanical, electrical, timing, and protocol requirements (including the physical attributes of I/O buses used to interconnect computers and peripheral devices) of the SCSI parallel interface will inter-operate. This allows several different peripherals (hard disk drives, removable disk drives, tape drives, CD-ROM drives, printers, scanners, optical media drives, and so on) to be added at the same time to a host computer without requiring modifications to the generic system hardware. For example, personal computers (PC""s or microcomputers), are inexpensive yet powerful enough to handle computationally-intensive user applications. The data storage and data sharing capabilities of PC""s are often expanded by externally coupling in a cluster environment, using SCSI protocol, as many as two such computers to a group of peripheral devices such as disk drives, tape drives, printers, and scanners. Capacity on a single SCSI bus is limited to 16: The host adapter of a SCSI controller takes up one slot in a PC (and, thus, only one IRQ) but can control up to 15 peripheral devices therefrom.
The working draft of the SCSI Parallel Interface-2 Standard (SPI-2), as modified, defines the cables, connectors, signals, transceivers, and protocol used to interconnect SCSI devices. The SPI-2 working draft states that a SCSI bus consists of all the conductors and connectors required to attain signal line continuity between every driver, receiver, and terminator for each signal. In operation, a SCSI bus is a bidirectional, multimaster bus which can accommodate peer to peer communications among multiple computer processing units (CPUs) and multiple peripheral devices. A SCSI device is a device (any computer peripheral) containing at least one SCSI port and the means to connect the drivers and receivers to the bus. SCSI bus termination is required at each end of a SCSI bus (and, thereby, defines an xe2x80x9cendxe2x80x9d of any SCSI bus) to set the negation state when no device is driving (this is called xe2x80x9cbiasingxe2x80x9d) and to match the impedance to that of the interconnect media. SCSI signal lines must be terminated at both ends with a terminator compatible with the type/protocol of transceivers (currently defined signal transmission mode protocols include SE/LVD or HVD) used in any connected SCSI device. A termination circuit that is delivering the performance requirements for such biasing and impedance matching is considered xe2x80x9cenabledxe2x80x9d. A switchable terminator is one that can be xe2x80x9cdisabledxe2x80x9d by disconnecting signal lines. The electrical connection directly between two terminators forms a bus path. Improper termination of a SCSI bus will very likely cause device malfunction. Any electrical path that is not part of the bus-path is a stub. The point where a stub meets the bus path is called a stub connection.
A SCSI primary bus is one that provides for and carries 8-bit or 16-bit data transfer. A SCSI secondary bus carries an additional 16-bit data bus that, when used in conjunction with a 16-bit primary bus, provides for a 32-bit data transfer path (although the latter is not, yet, widely used). SCSI devices may connect to a bus via 8-bit, 16-bit, or 32-bit ports. To date, SCSI parallel interface devices may be implemented with either 50, 68, or 80 pin connectors (whether shielded or unshielded). Eight-bit devices are referred to as xe2x80x9cnarrowxe2x80x9d devices (carried by 50 pin cables and connectors) and devices which permit parallel transfer of 16-bits or 32-bits at a time are called xe2x80x9cwidexe2x80x9d devices (carried by cables and connectors with at least 68 pin). Narrow and wide, as used in connection with SCSI compliant systems, refers to width of the data path. Data travels fast over SCSI buses, with Ultra SCSI data transfer speeds up to 40 MBps, wide Ultra2 LVD up to 80 MBps, and wide Ultra3 up to 160 MBps. Active termination of the xe2x80x9chigh bytexe2x80x9d must be accomplished if one is to connect a wide (16- or 32-bit transfer using 68 or more pin cable/connector) device to a narrow cable or device (8-bit transfer using 50 pins). As it is well known, a typical data transfer operation over a SCSI bus between a SCSI controller (or xe2x80x9chost adapterxe2x80x9d) located in a host computer system, to a target device (such as a disk drive) has seven SCSI xe2x80x9cphasesxe2x80x9d: (1) ARBITRATION, (2) SELECTION, (3) RESELECTION, (4) COMMAND, (5) DATA, (6) STATUS and (7) MESSAGE. For example, during the COMMAND phase, a SCSI command is transferred from the host adapter to a target (drive); and so on. Host adapter functional circuitry is typically maintained on a host bus adapter (HBA) chip on a printed circuit board structure referred to as a host adapter board (HAB) for connection to a PC host via an expansion slot. California based Adaptec, Inc., as well as the assignee hereof, design and distribute host adapters for making narrow to wide SCSI connections.
There is a patented xe2x80x98one chip bus master host adapter integrated circuitxe2x80x99 specifically designed for (i) connecting a first bus having a specified protocol for transferring information over the first bus and a first data transfer speed to a second bus having a specified protocol for transferring information over the second bus and a second data transfer speed, and (ii) transferring information between the two buses. This bus master host adapter integrated circuit (referred to in the patent as simply a xe2x80x98host adapterxe2x80x99) includes a reduced instruction set computing (RISC) processor which controls operations allowing the host adapter to function as a high speed bus master. The patented host adapter includes many features found in traditional add-in card SCSI host adapters: Bus master transfers, fast/wide SCSI, one interrupt per command, scatter/gather, overlapped seeks, tagged queuing, etc.
Transceivers transmit and receive electrical signals/information on a SCSI bus using single-ended (SE) signal transmission mode protocol or a differential protocol (either high voltage differential, HVD, or low voltage differential, LVD). Since the SE and HVD alternatives are mutually exclusive and the LVD and HVD alternatives are mutually exclusive, a bus can support only all HVD devices or SE/LVD signal transmission devices. In addition to SE, LVD, HVD transceivers and terminators, SE/LVD multimode transceiver and multimode terminator architecture has been designed for operation over a SCSI bus in the event it""s expected that a combination of SE and LVD protocol devices will be combined thereon. The SE/LVD multimode architecture allows for either SE- or LVD-mode signals depending upon input information sensed regarding respective mode operation via DIFFSENS. Since damage can occur to a SCSI device if a HVD device is plugged into a bus containing a SE/LVD multimode transceiver, or either an SE or LVD transceiver, signal line and interconnect media protocol used over, as well as termination at the end of, each SCSI bus must be appropriately configured. In a standardized SCSI connector pin arrangement, one pin is a dedicated DIFFSENS pin for transmission mode detection: The DIFFSENS pin is generally grounded in devices operating under SE protocol so that no electrical signal is present in the DIFFSENS line. Section 7.2.5 entitled xe2x80x9cSE/HVD transmission mode detectionxe2x80x9d, and particularly Table 32, of the Working Draft SCSI Parallel Interface-2 describes requirements for DIFFSENS receiver operation for each mode.
Fibre Channel is an emerging technology capable of transferring data as fast or faster than an Ultra3 SCSI system can, over fiber optic cabling as well as copper transmission media. Fiber Channel-type host bus adapters are installed into a host computer expansion slot just as SCSI HAB""s are installed. Fibre channel connections are often associated with the term xe2x80x9cloopxe2x80x9d (from the name Fibre Channel arbitrated loop) rather than xe2x80x9cbusxe2x80x9d (as SCSI devices are connected). There are actually other types of Fibre Channel connections, called xe2x80x9cpoint to pointxe2x80x9d and xe2x80x9cfabric.xe2x80x9d With fibre channel, communication between hosts and devices does not have to be done directly. Instead, users can employ hubs and switches between devices on the Fibre Channel network. Hubs and switches can be used to create Fibre Channel xe2x80x9cstorage networksxe2x80x9d. Fibre Channel cabling can be copper (which can go up to 30 meters) or fiber optic (currently up to 10 Km). In addition, no termination is necessary for fibre channel as is required in SCSI. Fiber optic ports directly placed on a peripheral device allow only for connections to fiber optic cabling. Commercially available adapters exist that allow a SCSI-compliant device to be connected to a Fiber Channel loop.
The assignee hereof has developed, and commercially distributes, a SYM2000(trademark) Storage Drive Module as part of its family of RAID storage products. The SYM2000(trademark) Module includes ten hot-swappable drive Customer Removable Units (CRUs) and two internal wide Ultra SCSI single-ended drive buses. The SYM2000(trademark) Module design only allows for a limited number of hardwire storage configuration possibilities: It automatically assigns SCSI device ID""s and incorporates the assignee""s (1) SYM53C141(trademark) SCSI Bus Expander chip which supports SE to SE bus expansion (in the xe2x80x9cRepeaterxe2x80x9d or xe2x80x9cExpanderxe2x80x9d mode of this chip) or SE to LVD bus conversion (the xe2x80x9cConverterxe2x80x9d mode), and (2) SYM53C120(trademark) SCSI Bus Expander chip which also supports SE to SE bus expansion and SE to HVD bus conversion. The SYM53C120(trademark) Bus Expander provides electrical isolation of the two SCSI buses (whether wide or narrow) between which it is sandwiched. Product reference materials are readily available for both of these Bus Expander chips, as well as the SYM2000(trademark) Module, all of which are hereby incorporated herein by reference. Additionally, the SYM2000(trademark) Module lacks other novel elements of the enclosure module of the invention, such as: an auto-termination control feature, software configurable bus (the SYM2000(trademark) bus is hardwired), a xe2x80x98manualxe2x80x99 data transfer width control feature, device power-ON/OFF feature for installed devices (i.e., must physically remove, devices to disconnect in the SYM2000(trademark)), incapable of supporting two different operational bus modes (devices connected to a SYM2000(trademark) enclosure have to be of the same transceiver mode), and a temperature control auto-monitoring feature (either fans are ON when SYM2000(trademark) enclosure is operating, or OFF when not). Without a reasonable solution at hand to manually configure the many functional features of a SCSI-compatible storage enclosure to accept the many different types of storage peripheral devices available, an electronic designer or computer technician can be severely limited in configuration design alternatives.
The new flexible enclosure module, described herein, is designed to accommodate synchronous operation of a wide range of electronic devices, utilizing the flexibility afforded a multi-bus enclosure design plus allowing optional manual configuration and re-configuration of one or more of the many operational features of SCSI storage devices. This innovative unit has the capacity for synchronous operation of several SCSI-compliant devices electrically connected to at least a first and second bus with a bus expansion logic element therebetween that allows for operation of the buses as a single logical bus (if each device is of only one type of transceiver mode, e.g., all SE/LVD or all HVD) or as independent buses (if the devices have transmission modes of both SE/LVE or HVD).
More specifically, unlike the enclosure systems currently available, the novel enclosure module and associated method incorporate a user interface for entering at least a first input for optional manual configuration of an operational feature thereof, and if the input is not properly registered for some reason, the module has been programmed to provide for automatic configuration of that, and other, operational feature(s) as appropriate. Additionally, to accommodate additional devices with one interface, two or more enclosure modules could be handily adapted for being controlled by a common user interface via the enclosures"" RS232 port, for example, in the spirit of the design goals suggested herein.
It is a primary object of this invention to provide an enclosure module for accommodating a plurality of peripheral devices that has a computerized control unit in electrical communication with a user interface and at least two buses with a bus expansion logic element therebetween that allows for operation of the buses as a single logical bus (if each device is of only one type of transceiver mode) or as independent buses as appropriate (if there is at least one device connected that is of another transceiver mode). The control unit is also in communication with termination circuitry for signal-appropriate bus termination and a first and second set of connectors (one for each of the two buses). It is also an object that a user interface for entering input for optional manual configuration of an operational feature of the enclosure module be included. It is also an object of this invention to provide an associated method of configuring a plurality of operational features, at least one of which can be done manually, of an enclosure module that can accommodate a plurality of peripheral devices. This method includes the steps of: entering, through the user interface, an input to manually configure at least one of the plurality of operational features; and if not properly registered, automatically configuring that operational feature.
The advantages of providing both the flexible new enclosure module and the new method of configuring a plurality of operational features, as described herein, follow:
(a) Key operational features (such as, a device ID for any one of, or all, the devices electrically connected to a corresponding connector; a SCSI signal transmission mode for any one of, or all, the devices so connected; pin-configuration of any one of, or all, connected devices; ON/OFF status of any the devices; the bus mode operation of the two buses (as a single logical bus or as independent buses), data transfer width of each device, enablement or disablement of signal-appropriate bus termination; and so on) can be manually configured, or reconfigured, via handy user interface by a technician familiar with mechanical, electrical, timing, and protocol requirement of SCSI parallel interface.
(b) Due to the many different configurations of disk and tape drives, printers, optical media drives, and other peripheral parallel-processing devices, and due to the fact that a device operating under SE/LVD and one that operates in a HVD environment cannot be operated along the same logical bus, it is desirable to have available in an enclosure, at least two logical busesxe2x80x94one for SE/LVD and the other for HVD if necessaryxe2x80x94as well as the capability to readily configure bus operation via programmed user interface.
(c) An xe2x80x98intelligentxe2x80x99 storage enclosure module programmed to check the system for incompatible/noncompliant configuration (whether done continuously or discretely at certain points throughout the process of configuring the enclosure) aids in reducing inadvertent component, device, or system failure.
(d) Module design flexibility and versatilityxe2x80x94Devices connected to the enclosure of the invention may be readily replaced and different SCSI devices having different operating characteristics can be added, and any associated re-configuration quickly performed, to an enclosure of the invention so that it can address storage problems in a wide variety of environments; and, two enclosures could be adapted for control by a common user interface.
(e) Design simplicity-Reducing overall fabrication costs, off-the-shelf bus expander and host adapter products available from the assignee hereof, plus LVD/SE and HVD terminator chips, control unit processing chips, and associated cabling are readily available for fabrication and programming according to the unique design and method of the invention to create the new enclosure module.
Briefly described, again, the invention includes an enclosure module for accommodating a plurality of peripheral devices. The module has: a computerized control unit in electrical communication with a user interface, a first and second bus with a bus expansion logic element therebetween that allows for operation of the buses as a single logical bus or as independent buses, termination circuitry for signal-appropriate bus termination, and a first and second plurality of connectors, each for electrical connection with one of the peripheral devices. The connectors are in communication with the buses. The user interface is for entering a first input for optional manual configuration of an operational feature of the enclosure module, and the module is programmed so that, if the input is not registered, the operational feature can be automatically configured without the particular information provided by the input. Key operational features include: a device ID for any one of, or all, the devices electrically connected to a corresponding connector; a SCSI signal transmission mode for any one of, or all, the devices so connected; pin-configuration of any one of, or all, connected devices; ON/OFF status of any the devices; the bus mode operation of the two buses (as a single logical bus or independent buses), data transfer width of connected devices, enablement or disablement of signal-appropriate bus termination; and so on. The first input can include, for example, the assigning of one device ID for each of the peripheral devices electrically connected, enablement of the signal-appropriate bus termination, causing an independent or separate logical bus operation, and so on.
Additional design features that further distinguish the module of the invention from known enclosure designs include: The user interface may also be capable of receiving a second, third, fourth, and so on, input for optional manual configuration of a second, third, fourth, respectively, operational feature of the enclosure module. The control unit can provide instructions to the bus expansion logic element (whether the bus expander is logically-defined outside thereof or considered a part of the control unit) for operation of the buses (as a single bus or independent buses) in the event input is either not entered, or entered but not properly registered. The termination circuitry can include a plurality of terminator IC elements, each positioned at a logical end of the buses for enabling, as necessary (whether done manually or automatically via the bus expansion logic element or control unit), the signal-appropriate bus termination. The connectors can each have a multi-connect assembly for connection with a first, second, and third type SCSI connector. The control unit can receive information (for example, from the HAB or from a xe2x80x98smartxe2x80x99 multi-connect assembly) about the SCSI signal transmission mode for each peripheral device electrically connected to instruct the bus expansion logic element for bus operation. The user interface may have a liquid crystal display (LCD) or other means for displaying status information about operational features such as bus operation (two independent or single bus) and associated mode (SE/LVD/HVD), device ID and status, and proper bus termination.
Also characterized herein is an associated method of configuring a plurality of operational features, at least one of which can be done manually, of an enclosure module that can accommodate a plurality of peripheral devices. The method of the invention has the steps of: providing a computerized control unit in electrical communication with a user interface, a first and second bus with a bus expansion logic element therebetween that allows for operation of the buses as a single logical bus or as independent buses, termination circuitry for signal-appropriate bus termination, and a first and second plurality of connectors, each for electrical connection with one of the devices; entering, through the user interface, a first input to manually configure at least one of the operational features; and if no such input is registered, automatically configuring the operational feature.
Additional design features that further distinguish the novel method include: detecting a signal transmission mode and a data transfer width for any one or more of the peripheral devices connected for SCSI-compliant operation of the buses; displaying status information of any incompatible configuration sensed by the enclosure; automatically reconfiguring an incompatible configuration (e.g., resolving conflicting device IDs), if sensed, to be SCSI-compatible; enabling a plurality of terminator integrated circuit (IC) elements of the termination circuitry to cause signal-appropriate bus termination; and so on.